@Misc{ 
  bucbuttre98,
  author = { Bucur, Dorin and Buttazzo, Giuseppe and Trebeschi, Paola },
  title = { An Existence Result for Optimal Obstacles },
  journal = {  },
  year = { 1998 },
  pages = {  },
  URL = { http://cvgmt.sns.it/paper/408/ },
  note = { cvgmt preprint}
}